The Gunn–Peterson effect and the Lyman alpha forest期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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The Gunn–Peterson effect and the Lyman alpha forest

Authors:	Sergei A Levshakov & Wilhelm H Kegel

Institution:	Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-01, Japan,;Department of Theoretical Astrophysics, A. F. Ioffe Physico-Technical Institute, 194021 St Petersburg, Russia,;Institut für Theoretische Physik der Universität Frankfurt am Main, Postfach 11 19 32, 60054 Frankfurt/Main 11, Germany

Abstract:	We show that spatial correlations in a stochastic large-scale velocity field in an otherwise smooth intergalactic medium (homogeneous comoving density) superposed on the general Hubble flow may cause a 'line-like' structure in QSO spectra similar to the population of unsaturated Lyα forest lines which usually are attributed to individual clouds with 10¹¹ ? N _{H i} 5 × 10¹³ cm^?2. Therefore there is no clear observational distinction between a diffuse intergalactic medium and discrete intergalactic clouds. It follows that the H i density in the diffuse intergalactic medium might be substantially underestimated if it is determined from the observed intensity distribution near the apparent continuum in high-resolution spectra of QSOs. Our tentative estimate implies a diffuse neutral hydrogen opacity τ_GP ～ 0.3 at z ～ 3 and a current baryon density Ω_IGM ? 0.08, assuming a Hubble constant H ₀ = 70 km s^?1 Mpc^?1.

Keywords:	line: formation line: profiles quasars: absorption lines